US 2002/0118730 A1 · Determining correlations of received sequences to multiple known sequences in a communications system

Abstract

A method, system, and apparatus enables interfering signals in a communications system to be efficiently identified using correlation calculations. Once identified, the interfering signals may be rejected and removed from further processing in a receiver. The number of mathematical operations required to determine correlates of multiple training sequences to received sequences (e.g., at multiple offsets) may be reduced by up to eighty percent (80%) in a Global System for Mobile Communications (GSM) implementation. In accordance with certain embodiments, a correlation equation is manipulated, for example, to eliminate certain products by ensuring that they equate to zero, to eliminate redundant calculations by recognizing repeated subsequences, to eliminate common subexpressions, to determine a negative of a correlation result, etc. The manipulated correlation equation is then utilized within a receiver.

Claims34

Dependent claims

A method for correlating a received sequence to known sequences in a communications system, comprising the steps of:

providing a plurality of known sequences of values;
receiving a sequence of values;
producing at least one reusable addend;
applying said sequence of values to each known sequence of values of said plurality of known sequences of values to produce respective sets of addends, each set of addends of said respective sets of addends corresponding to a respective known sequence of values of said plurality of known sequences of values and including said at least one reusable addend;
determining respective correlation results responsive to said respective sets of addends, each respective correlation result corresponding to a correlation between said sequence of values and a respective known sequence of values of said plurality of known sequences of values;
and
wherein said each set of addends of said respective sets of addends have been reduced in number utilizing a common subexpression elimination algorithm.

4 more elements

A method for correlating a received sequence to a known sequence in a communications system, comprising the steps of:

receiving a sequence of values;
applying said sequence of values to at least one known sequence of values in a correlation equation, said correlation equation definable as including a sum of products of said sequence of values and said at least one known sequence of values;
and
determining a correlation result of a manipulated version of said correlation equation, said manipulated version of said correlation equation derived from performing at least two of the following modifications:
said correlation equation modified so that at least one product of said sum of products of said correlation equation becomes zero;
said correlation equation modified to produce a sum that is independent of said at least one known sequence of values;
said correlation equation, wherein said at least one known sequence of values includes a known number of values and at least two identical subsequences of values, modified such that a number of product addends of said sum of products of said correlation equation is less than said known number of said known number of values of said at least one known sequence of values by eliminating products corresponding to one of said at least two identical subsequences of values of said at least one known sequence of values;
said correlation equation and terms thereof modified so as to eliminate common subexpressions;
and
said correlation equation modified such that a negative result of said correlation equation is to be calculated.

7 more elements

A communication station for correlating a received sequence to a known sequence in a communications system, the communication station comprising:

a receiver, said receiver adapted to receive a sequence of values;
a processing unit operatively connected to said receiver, said processing unit adapted to apply said sequence of values to at least one known sequence of values in a correlation equation, said correlation equation definable as including a sum of products of said sequence of values and said at least one known sequence of values;
said processing unit operable to determine a correlation result of a manipulated version of said correlation equation, said manipulated version of said correlation equation derived as a result of performing at least two of the following modifications:
modify said correlation equation so that at least one product of said sum of products of said correlation equation becomes zero;
modify said correlation equation to produce a sum that is independent of said at least one known sequence of values;
modify said correlation equation, wherein said at least one known sequence of values includes a known number of values and at least two identical subsequences of values, such that a number of product addends of said sum of products is less than said known number of said known number of values by eliminating products corresponding to one of said at least two identical subsequences of values;
modify said correlation equation and terms thereof so as to eliminate common subexpressions;
and
modify said correlation equation such that a negative result of said correlation equation is to be calculated.

6 more elements

A communication station for correlating a received sequence to a known sequence in a communications system, the communication station comprising:

a receiver, said receiver adapted to receive a sequence of values;
a memory, said memory storing a plurality of known sequences of values;
a processing unit operatively connected to said receiver and said memory, said processing unit programmed to compute a plurality of correlation results between said sequence of values and said plurality of known sequences of values;
and
wherein said processing unit is configured to compute said plurality of correlation results using a modified correlation equation.

2 more elements

Dependencies are inferred from the claim text.

Determining correlations of received sequences to multiple known sequences in a communications system

Life of this patent

Determining correlations of received sequences to multiple known sequences in a communications system

Life of this patent

Abstract

Claims34